Method and drilling apparatus for down-the-hole drilling

ABSTRACT

A method and drilling apparatus for drilling. The drilling is carried out by a drilling apparatus including a drilling device including a casing part and at least during drilling a drilling unit. At the drilling head of the drilling apparatus are at least first drilling elements, a second drilling element, a flushing flow arrangement and a pressure medium operated hammering device. The first drilling elements are coupled with the second drilling element power-transmittedly in order to carry out cooperation thereof at least during drilling with the second drilling elements for a rotational motion, a feeding motion and the hammering motion, and are coupled removably to enable removal thereof from the hole. For producing the hammering motion a hammering device is used that is operated essentially by a water-based pressure medium. At least a part of the water-based pressure medium operating the hammering device is used as the flushing medium.

The invention relates to a method and drilling apparatus for down-the-hole drilling according to the preambles of the independent claims.

For example in patent publication FI 75650 there has been presented a boring tool, which is meant for boring and/or hammer drilling, to be used in connection with a drill rod unit placed inside a mantle pipe. The boring tool to be attached at the front end of the drill rod unit has a center drill, being provided with a cutting unit, and an eccentric reaming drill, being placed after the center drill, the reaming drill having also a cutting unit. The reaming drill moves with respect to the center drill between a drilling position, in which it is positioned sidewards in front of the mantle pipe, and a return position, in which it is withdrawn in radial direction inside the mantle pipe. Deviating from earlier solutions, in which the center drill is in most cases provided with four cutting parts directed radially and being made of hard metal, the reamer for its part comprising either one or two radially directed cutting parts made of hard metal, in the solution according to the publication in question, the cutting parts are replaced by bit parts being arranged in a certain manner. With the solution presented in this publication such constructions of the center drill and the reaming drill have been aimed that the operating time of the boring tool will be as long as possible.

A way to carry out overburden drilling in a more developed manner compared to prior art, is formerly known e.g. from Finnish Patent No. 95618. The drilling head of the drilling unit of the drilling apparatus existing inside a casing part or in other words a so called casing pipe according to this patent, is formed of a first frame part and an annular second frame part, in the drilling surfaces of which there has been arranged drilling organs, such as drill bits or like, of the first and second drilling means or in other words of the pilot and the reamer. In this solution the first drilling means that is the first frame part forming the pilot, is being released from the second frame part forming the reamer in order to pull the same alone off from a drilled hole after the drilling situation. In the solution in question the second organs of the flushing means for removal of drilling waste being generated are arranged to lead drilling waste by means of an assembly belonging to the counterpart surface arrangement, which connects the said drilling means together for a drilling situation unrotatively in respect with each other and in both directions longitudinally, which, in other words, is being carried out as an advantageous embodiment by loosening grooves, belonging to a bayonet coupling, placed longitudinally in the outer periphery of the first frame part.

At present significant problems are involved particularly with a so called casing drilling e.g. for micro piles or anchors, regarding which improvements in the down-the-hole (DTH) drilling have been continuously attempted to search for. In this connection, a problem particularly in performing drilling with a pressure medium operated hammering device or an air hammer (DTH) is the fact that flushing air is aimed directly at a drilled surface. In this case, the pressurized air may penetrate the soil, whereby depending on the nature of the soil, it may get drifted to the surrounding structures and thus certain circumstances cause changes to weight-carrying capacity of structures under strain in the environment by eliminating/decreasing load capacity of e.g. friction piles. On the other hand, removing of air through a ring-shaped surface between the earth pipe and the drilling equipment or along an exhaust line of double-wall pipes causes furthermore counter pressure, which also makes easier drifting of pressurized air into the soil. Lots of damages have been caused by using pressurized air in DTH-drilling, which is why on certain sites it is at present not at all allowed any more to use a pneumatic down-the-hole hammer.

In order to decrease harmful effects of pressurized air, it is in principle possible to carry out drilling also by a so called DFS-system, in which the down-the-hole drill is of so called RC-(Reverse Circulation) type and, which uses pressurized air in the hammering device and possibly water or some other medium for flushing, in which case the flushing medium is lead to outside of the air hammer and the casing to be drawn. Experiences of this kind of drilling have, however, shown that it has not been possible to keep the pressurized air within the internal circulation of the casing pipe, but instead it penetrates also harmfully out from the earth pipe, which is why the system in question has not become general due to its unreliability. In addition to the above, double-wall drill pipes being used in this kind of drilling are disproportionately heavy, which is why they can not be lifted manually, whereby in all drilling sites there is not very often even space for separate lifting devices.

For the above reasons, particularly use of a so called water hammer has become general in sites, where there is a fear of air damaging structures close by or disturbing soil so that its weight-carrying capacity will get essentially decreased. The water hammer uses usually a large amount of pressurized water, but it does not cause the same kind of decreasing of friction in the surrounding structures like an air hammer.

In patent publication FI 111408 there has been presented a method, device and drill bit to be used in down-the-hole drilling in the installation of a casing, wherein the casing is being installed next to the drill bit to the bore formed by the drill bit and wherein drilling waste that gets generated during drilling is removed by flushing medium, being brought through the drill bit. In the solution in question, drill mud or a like flowing medium is being used advantageously as the flushing medium, which is being led from the drilling point along with the drilling waste at least partly upward along with the outer surface of the casing.

The implementation of the solution mentioned above has not been developed enough, either, because it is first of all still based on utilization of pressurized air as the medium for operating the hammer device, which is why the drilling device's constructions require multi-layer structures and very carefully implemented sealings in order to prevent drifting of pressurized air into the soil, the sealings requiring regular service and maintenance.

It is an aim of the method and drilling apparatus according to the present invention to achieve a decisive improvement in the problems described above and thus to raise essentially the level of prior art. In order to carry out this aim, the method and drilling apparatus according to the invention are mainly characterized by what has been presented in the characterizing parts of the independent claims related thereto.

As the most important advantages of the method and drilling apparatus according to the invention may be mentioned simplicity and efficiency of the constructions and operating principles enabled by the same first of all thanks to the fact that use of pressurized air can be totally avoided, and on the other hand thanks to the fact that one and the same water based medium can be used both for the hammering and the flushing. One crucial advantage of the method according to the invention is also the fact that the water based medium being used for flushing packs substance loosened from the soil upward along a narrow channel drilled around the casing part or in other words the casing pipe so that it simultaneously tightens the surrounding soil by aid of operating vibration of the hammering device or in other words the hammer and the loosened ground substance. When the flushing takes place externally, over drilling (which means that more mass would be removed from the ground than what the space of the pipe to be drawn into the hole requires) does not take place in a corresponding manner as in traditional implementations, because the channel that is formed during drilling is small and the pressure of the soil prevents it from spreading. In this respect particularly in normal flushing taking place internally within the pipe, removal of drilling waste must be carried out when using both air and water operated hammers in practice by dimensioning the flushing oversized, so that getting clean of the channel is made sure by a high enough flushing flow. This is necessary also for such a reason that the hammer with its equipment can be drawn on time out from the casing pipe. When the flushing is increased in this way, over drilling is thus again increased, whereby it is not possible to estimate the amount of removed drilling waste during drilling, which is why one can estimate quantity of cavities caused to the ground or of loosening of the ground only after possible falls of earth have already taken place. When using the method and drilling apparatus according to the invention, this danger does not exist any more and the piping of the drilling device is always totally empty from drilling waste, which is why the drill unit along with its hammer, drill bits and rods can always be easily removed. The method and drilling apparatus according to the invention have furthermore a significant influence also in improvement of work efficiency thanks to making the drilling more efficient.

Other advantageous embodiments of the method and drilling apparatus according to the invention have been presented in the dependent claims related thereto.

In the following description the invention is depicted in detail with reference to the appended drawings, in which

in FIG. 1 is shown as a longitudinal cross-section a general operating principle of an advantageous drilling apparatus exploiting the method according to the invention,

in FIG. 2 is shown as a longitudinal cross-section an advantageous implementation of a drilling head of the drilling apparatus according to the invention,

in FIG. 3 is shown a drilling surface of the implementation shown in FIG. 2 as seen from the front, and

in FIG. 4 is shown as a longitudinal cross-section furthermore one advantageous drilling head of the drilling apparatus as an alternative to the one shown in FIG. 2.

The invention relates first of all to a method for down-the-hole drilling that is carried out by a drilling apparatus, having a drilling device 1 that comprises a casing part 2 and at least during a drilling situation an essentially inside thereof existing drilling unit 3, at the drilling head of which there are at least first drilling means 4 for drilling a center hole, second drilling means 5 for reaming the center hole for the casing part 2, a flushing flow arrangement 6 for leading of drilling waste by influence of the flushing medium to outside of the drilling device, at least partly upward along the outer surface of the drilling device 1, and a hammering device operated by pressure medium for transmitting of a hammering motion t4 to the drilling means 4, 5 for drilling. The first drilling means 4 are coupled with the second drilling means 5 first of all power-transmittedly in order to carry out cooperation thereof at least during a drilling situation with the second drilling means 5 for a rotational motion w4, a feeding motion z4 and the hammering motion t4, and on the other hand removably in order to enable removal thereof from the hole. The casing part 2 is furthermore arranged to be drawn to a hole to be drilled by the drilling unit 3. For producing the hammering motion t4, a hammering device 7 is being used that is operated essentially by a water-based pressure medium, whereby at least a part of the water-based pressure medium is being used furthermore as the flushing medium in the drilling.

The method according to the invention is being applied for advantageously when operating with a drilling apparatus, the drilling head of which consisting of with reference to those advantageous embodiments shown as alternative constructions e.g. in FIGS. 2 and 4 a first frame part 4 a and a second frame part 5 a, whereby the drilling surfaces of the said frame parts are provided with drilling organs of the first and the second drilling means 4, 5, such an integrated drilling part, separate drilling pieces, bits or like, whereby flushing medium is being led to the drilling head internally in the drilling device 1, such as through a drill rod/rods pt and the drilling unit 3 and, whereby a casing shoe 8 is being exploited in order to couple the drilling unit 3 with an end of the casing part 2. For producing the hammering motion t4 with respect to the casing part 2 an internal hammering device is being exploited that is placed at the end of a drill rod or rods pt, at a back part of the drilling unit 3. At least a part of the water-based pressure medium operating the hammering device 7 is being lead on the principle manifested e.g. in FIG. 1 by the flushing flow arrangement 6, such as by transmission of a flow channel 6 a existing at the center of the drilling unit 3 or correspondingly to the first and/or the second drilling means 4, 5, such as to the drilling surface/surfaces of the first and/or the second frame parts 4 a, 5 a and by guidance of flow grooves 6 b or like in the frame part/parts 4 a, 5 a furthermore radially at an outer periphery of the drilling device 1 in order to assist drifting thereof to outside of the casing part 2.

As a further advantageous embodiment of the method according to the invention water, water-polymer mixture, water-bentonite mixture and/or like is being used as the water-based pressure and flushing medium.

Particularly with reference to FIGS. 2 and 3, a reamer is being used as the second drilling means 5 that is rotationally symmetrical and that has an essentially continuing drilling surface radially, when viewed in a cross-section perpendicular to a longitudinal direction s of the drilling unit 3. Furthermore with reference to the alternative embodiment shown in FIG. 4, a reamer is being used as the second drilling means 5 that operates on eccentric principle, being non-symmetrical and that opens radially outwards for drilling.

The invention relates also to a drilling apparatus meant for down-the-hole drilling that has a drilling device 1, having a hammering device 7 that operates essentially by a water-based pressure medium, such as water, water-polymer mixture, water-bentonite mixture and/or like, and wherein at least a part of the water-based pressure medium operating the hammering device 7 is arranged furthermore to be utilized as a flushing medium in the drilling.

As an advantageous embodiment of the drilling apparatus according to the invention at least a part of the water-based pressure medium operating the hammering device 7 is lead by the flushing flow arrangement 6, such as by transmission of a flow channel 6 a existing at a center of the drilling unit 3 or correspondingly, to the first and/or the second drilling means 4, 5, such as to the drilling surface/surfaces of the first and/or the second frame parts 4 a, 5 a, and furthermore by guidance of flow grooves 6 b or like in the frame part/parts 4 a, 5 a radially at an outer periphery of the drilling device 1 in order to assist drifting thereof to outside of the casing part 2.

With reference to the advantageous embodiment shown in FIGS. 1, 2 and 3, the second drilling means 5 comprise a reamer that is rotationally symmetrical and that has an essentially continuing drilling surface radially, when viewed in a cross-section perpendicular to a longitudinal direction s of the drilling unit 3. Correspondingly as an advantageous embodiment with reference to the alternative implementation shown in FIG. 4, the second drilling means 5 comprise a reamer that operates on eccentric principle, being non-symmetrical and that opens radially outwards for drilling.

It is clear that the invention is not limited to the embodiments, being presented or described above, but instead it can be modified within the basic idea of the invention according to the needs at any given time. It is thus clear that the constructions of the drilling heads being illustrated in the appended drawings may vary in practice very much merely when being carried out with differing diameters. As the drilling device it is instead of the type of embodiments shown in FIG. 2 or 4 naturally possible to use also other drilling devices that are applicable for the same purpose, in which a casing part is being exploited in connection with the drilling that is most advantageously not rotated when being drawn into the ground. It is not that significant for the method and the drilling apparatus according to the invention, either, how the first and second drilling means are coupled to work, so that most heterogeneous solutions can be exploited as power transmission assemblies between the same starting from a screw joint locking. Also the casing shoe can be placed in an integrated manner at the end of the casing part etc. Furthermore e.g. on the principle shown in FIG. 1, it is possible to complement the flushing flow arrangement e.g. by a flow pipe connected to the space between the casing part and the drilling unit e.g. in order to keep the space surrounding the drilling unit empty, and/or by a flushing assembly that greases the joint between the drilling means and the casing shoe. 

1. A method for down-the-hole drilling, the drilling being carried out by a drilling apparatus, having a drilling device that comprises a casing part and at least during a drilling situation an essentially inside thereof existing drilling unit, at the drilling head of which there are at least; a first frame part, a drilling surface of which being provided with first drilling means for drilling a center hole; a second frame part, a drilling surface of which being provided with second drilling means for reaming the center hole for the casing part; a flushing flow arrangement first of all for leading of flushing medium into the drilling head internally in the drilling device, such as through a drill rod/rods and the drilling unit, and on the other hand for leading of drilling waste by influence of the flushing medium to outside of the drilling device, at least partly upward along the outer surface of the drilling device; and with respect to the casing part an internal pressure medium operated hammering device, being placed at an end of a drill rod or rods, at a back part of the drilling unit in order to transmit a hammering motion to the drilling means for drilling, whereby the first drilling means are coupled with the second drilling means first of all power-transmittedly in order to carry out cooperation thereof at least during a drilling situation with the second drilling means for a rotational motion, a feeding motion and the hammering motion, and on the other hand removably in order to enable removal thereof from the hole, whereby the casing part is arranged to be drawn to a hole to be drilled by the drilling unit without rotating the casing part around its longitudinal axis, whereby for producing the hammering motion a hammering device is being used that is operated essentially by a water-based pressure medium and, whereby at least a part of the water-based pressure medium operating the hammering device is used for flushing, wherein the water-based pressure medium is led from the hammering device by the flushing flow arrangement, such as by transmission of a flow channel existing at a center of the drilling unit, to the first and the second drilling means, such as to the drilling surfaces of the first and the second frame parts.
 2. The method according to claim 1 when operating with a drilling apparatus, wherein the drilling organs of the first and the second drilling means comprise an integrated drilling part, separate drilling pieces, bits or like and, wherein a casing shoe is being exploited for coupling of the drilling unit with an end of the casing part, wherein at least a part of the pressure medium operating the hammering device is being lead by guidance of flow grooves or like in the frame part/parts furthermore radially at an outer periphery of the drilling device in order to assist drifting thereof to outside of the casing part.
 3. The method according to claim 1, wherein water, water-polymer mixture, water-bentonite mixture and/or like is being used as the water-based pressure and flushing medium.
 4. The method according to claim 1, wherein a reamer is being used as the second drilling means that is rotationally symmetrical and that has an essentially continuing drilling surface radially, when viewed in a cross-section perpendicular to a longitudinal direction(s) of the drilling unit.
 5. The method according to claim 1, wherein a reamer is being used as the second drilling means that operates on eccentric principle, being non-symmetrical and that opens radially outwards for drilling.
 6. A drilling apparatus for down-the-hole drilling that has a drilling device, comprising a casing part and at least during a drilling situation an essentially inside thereof existing drilling unit, at the drilling head of which there are at least; a first frame part, a drilling surface of which being provided with first drilling means for drilling a center hole; a second frame part, a drilling surface of which being provided with second drilling means for reaming the center hole for the casing part; a flushing flow arrangement first of all for leading of flushing medium into the drilling head internally in the drilling device, such as through a drill rod/rods and the drilling unit, and on the other hand for leading of drilling waste by influence of the flushing medium to outside of the drilling device, at least partly upward along the outer surface of the drilling device; and with respect to the casing part an internal pressure medium operated hammering device, being placed at an end of a drill rod or rods, at a back part of the drilling unit in order to transmit a hammering motion to the drilling means for drilling, whereby the first drilling means are coupled with the second drilling means first of all power-transmittedly in order to carry out cooperation thereof at least during a drilling situation with the second drilling means for a rotational motion, a feeding motion and the hammering motion, and on the other hand removably in order to enable removal thereof from the hole, whereby the casing part is arranged to be drawn to a hole to be drilled by the drilling unit without rotating the casing part around its longitudinal axis, whereby the drilling device of the drilling apparatus has a hammering device that operates essentially by a water-based pressure medium, and, whereby at least a part of the water-based pressure medium operating the hammering device is used for flushing, characterized in that the flushing flow arrangement, such as a flow channel existing at a center of the drilling unit, is arranged to lead the water-based pressure medium, such as water, water-polymer mixture, water-bentonite mixture and/or like from the hammering device to the first and the second drilling means, such as to the drilling surfaces of the first and the second frame parts.
 7. The drilling apparatus according to claim 6, wherein the drilling organs of the first and the second drilling means comprise an integrated drilling part, separate drilling pieces, bits or like and, wherein a casing shoe is being exploited for coupling of the drilling unit with an end of the casing part, characterized in that wherein at least a part of the pressure medium operating the hammering device is lead by guidance of flow grooves or like in the frame part/parts radially at an outer periphery of the drilling device in order to assist drifting thereof to outside of the casing part.
 8. The drilling according to claim 6, wherein the second drilling means comprise a reamer that is rotationally symmetrical and that has an essentially continuing drilling surface radially, when viewed in a cross-section perpendicular to a longitudinal direction(s) of the drilling unit.
 9. The drilling apparatus according to claim 6, wherein the second drilling means comprise a reamer that operates on eccentric principle, being non-symmetrical and that opens radially outwards for drilling. 